Aqueous alkali metal or ammonium silicate compositions containing inorganic curing agents are known. See, for example, Neely, U.S. Pat. No. 4,288,252.
In general, the prior art uses alkali silicates that are cross-linked with B-form aluminum trimetaphosphate. Cross-linking of the alkali silicate is attained by heating an article coated with the aqueous composition to an elevated temperature of 400.degree. F. or higher.
The aqueous composition is made by mixing alkali silicate with fillers and/or pigments and placing the mixture in a sealed container. The B-form aluminum trimetaphosphate is mixed in water with or without pigments and fillers and stored in a second sealed container. Prior to use, the separate materials are mixed together. The separate containers are necessary since the B-form aluminum trimetaphosphate and alkali silicates undergo a non-cross-linking reaction even at room temperature to produce a solidified mass within about one day. Once the materials from the separate containers are mixed, the resulting inorganic paint composition must be used within about eight hours. Thus, the paint system must be prepared as a two pack system to prevent this undesirable reaction.